SMEX03 Surface and Soil Temperature Measurements: Alabama

Summary

This data set contains land surface temperature and soil temperature data at depths of 1 cm, 5 cm, and 10 cm collected during the Soil Moisture Experiment 2003 (SMEX03). Data were collected from 21 June 2003 to 2 July 2003 in northern Alabama and southern Tennessee, USA at crop, pasture, and forested sites. Data are provided in a Microsoft Excel spreadsheet and an ASCII text file, and are available via FTP.

These data were collected as part of a validation study for the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E). AMSR-E is a mission instrument launched aboard NASA's Aqua Satellite on 04 May 2002. AMSR-E validation studies linked to SMEX are designed to evaluate the accuracy of AMSR-E soil moisture data. Specific validation objectives include assessing and refining soil moisture algorithm performance; verifying soil moisture estimation accuracy; investigating the effects of vegetation, surface temperature, topography, and soil texture on soil moisture accuracy; and determining the regions that are useful for AMSR-E soil moisture measurements.

Citing These Data

Crosson, William and Charles Laymon. 2007. SMEX03 Soil Moisture and Temperature Measurements: Alabama. Boulder, Colorado, USA: National Snow and Ice Data Center. Digital media.

Overview Table

Category	Description
Data format	Microsoft Excel file Tab-deliminated ASCII text file
Spatial coverage and resolution	Southernmost Latitude: 34.68º N Northernmost Latitude: 35.16º N Westernmost Longitude: 87.07º W Easternmost Longitude: 85.78º W
Temporal coverage and resolution	21 June 2003 to 2 July 2003 Measurements were made daily.
File naming convention	Soil_Temps_AL.xls Soil_Temps_AL.txt
File size	35 KB to 111 KB
Parameter(s)	Land surface temperature Soil temperatures at 1 cm, 5 cm, and 10 cm
Procedures for obtaining data	Data are available via FTP.

Table of Contents

1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information

1. Contacts and Acknowledgments

Investigator(s)

William Crosson
Universities Space Research Association
Global Hydrology and Climate Center
NASA Marshall Space Flight Center
Hunstville, AL 35812
USA

Charles Laymon
Universities Space Research Association
Global Hydrology and Climate Center
NASA Marshall Space Flight Center
Hunstville, AL 35812
USA

Technical Contact

Acknowledgements

The investigators would like to acknowledge Frank Archer, Karnita Golson, Linda Cornett, Alabama A&M University, and the many Alabama A&M students, faculty,and staff members who collected and processed the field data.

2. Detailed Data Description

Format

Data are provided in a Microsoft Excel file and as a tab-delimited ASCII text file. The text file contains the same data as the Excel file. Table 1 lists the column headings and data field descriptions for the files.

Table 1: Column Headings and Data Field Descriptions

Column Heading	Units	Description
Date	MM/DD/YY	Date of measurements
DOY	DDD	Numerical day of year (Julian Date)
Time	HH:MM	Time of day in Central Daylight Time (CDT)
Site	-	Site number (1-59)
Lat	decimal degrees	Latitude of site
Long	decimal degrees	Longitude of site
Surface	°C	Land surface temperature
1 cm	°C	Soil temperature at 1 cm depth
5 cm	°C	Soil temperature at 5 cm depth
10 cm	°C	Soil temperature at 10 cm depth

 

File Naming Convention

The Excel file is named Soil_Temps_AL.xls. The ASCII text file is named Soil_Temps_AL.txt.

File Size

The Excel file is 111 KB. The ASCII text file is 35 KB.

Spatial Coverage

Southernmost Latitude: 34.68 º N
Northernmost Latitude: 35.16º N
Westernmost Longitude: 87.07º W
Easternmost Longitude: 85.78º W

Temporal Coverage

Data were collected from 21 June 2003 to 2 July 2003.

Temporal Resolution

Temperature readings were taken daily. 

Parameter or Variable

Parameter Description

Parameters in this data set are land surface temperature (°C) and soil temperature ( °C) at depths of 1 cm, 5 cm, and 10 cm. A daily mean was calculated for each variable.

Sample Data Record

The following sample shows the first five rows of the Soil_Temps_AL.txt file.

Date	DOY	Time	Site	Lat	Long	Surface	1 cm	5 cm	10 cm
6/22/03	173	12:55	1	35.1114	-87.0021	36.0	33.5	32.2	27.3
6/22/03	173	11:24	2	35.1254	-86.8723	32.0	26.5	24.3	24.1
6/22/03	173	12:37	3	35.0505	-86.9961	48.0	29.7	26.6	25.2
6/22/03	173	12:00	4	35.0428	-86.8654	25.0	30.7	29.5	28.4

Error Sources

Due to breakage of the soil temperature sensors in hard soils, some sites were not sampled on particular days. Enough sensors broke to deplete the supply of spares, resulting in several sites not being sampled during the last few days of the experiment. Data that were not collected are flagged as -9999. Errors in land surface temperature are related mainly to representativeness of the readings. Variability at a given site could be extremely large (> 20° C), particularly for crop sites which comprised a mixture of bare soil and vegetation, therefore a single reading may not represent the mean land surface temperature very well.

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

The total volume of all data files is 146 KB.

Related Data Collections

• AMSR-E Soil Moisture Validation Data: Other data sets from SMEX campaigns available at NSIDC.
• AMSR-E/Aqua Data at NSIDC: AMSR-E standard data products available at NSIDC.

4. Data Acquisition and Processing

Sensor or Instrument Description

Investigators used a Raytek Raynger MT4 MiniTemp hand-held infrared thermometer to measure land surface temperature. The instrument has a range of -18°C to 400°C and a pre-set emissivity of 0.95. Accuracy is ±2 percent of reading or ±2°C, whichever is greater, for targets at -1°C to 260°C, and ±3°C for targets at -18°C to -1°C. Visit the Raytek Web site for more information. Soil temperatures were measured with a Taylor Switchable Digital Pocket Thermometer. Visit the Taylor Web site for more information.

Data Acquisition Methods

Data were collected at 59 locations in Alabama and southern Tennessee which included crop, pasture, and forested sites. Surface temperature measurements were made daily at each of the sites and recorded in field books. The infrared thermometers were pointed at the ground at a near-nadir angle. The protocol was for several readings to be made and an average recorded, but some teams took only a single reading. Soil temperatures were measured daily at depths of 1 cm, 5 cm, and 10 cm for each of the field sites. The thermometer was inserted vertically into the soil and allowed time for stabilization at each depth. Values were recorded in the field books. For AMSR-E validation purposes, temperatures were measured each day between 11:00 a.m. and 3:00 p.m. CDT.

5. References and Related Publications

Please see the USDA SMEX03 Web site for in depth information on the science mission and goal of the SMEX project.

6. Document Information

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document.

AMSR-E	Advanced Microwave Scanning Radiometer - Earth Observing System
ASCII	American Standard Code for Information Interchange
CDT	Central Daylight Time
FTP	File Transfer Protocol
NASA	National Aeronautics and Space Administration
NSIDC	National Snow and Ice Data Center
SMEX	Soil Moisture Experiment
URL	Uniform Resource Locator

Document Creation Date

October 2007

Document URL

http://nsidc.org/nsidc0319_smex03_soil_temp_al.gd.html